1. Technical Field
The present invention relates to a flexural vibration piece, a flexural vibrator, and an electronic apparatus, which have configurations suitable for downsizing.
2. Related Art
To date, a flexural vibration piece has been disclosed which includes a pair of piezoelectric elements spaced apart on the front surface of a vibrating arm, as disclosed in, for example, JP-A-2008-11348. The flexural vibration piece is such that, by a drive voltage being applied to each of the piezoelectric elements, and each of the piezoelectric elements being deformed, the vibrating arm is caused to flex in a predetermined direction. In this case, the piezoelectric elements, being of a configuration wherein a piezoelectric layer is sandwiched by two electrodes, are such that the drive voltage is applied to the two electrodes, deforming the piezoelectric layer. Also, a configuration has also been disclosed wherein a further pair of piezoelectric elements are provided on the rear surface on the side opposite the front surface, according to which, it is possible to cause the vibrating arm to flex more efficiently. That is, the flexural vibration piece is such that as the piezoelectric elements, which are of a film with good piezoelectric characteristics, are formed on the vibrating arm, and the vibrating arm is caused to flex by deforming the piezoelectric elements, there are less restrictions with respect to the shape of the vibrating arm, and a downsizing is also possible.
Herein, as a restriction with respect to the shape of the vibrating arm, for example, the formation in a vibrating arm which is of a piezoelectric material of a groove for widening an electrode region in order to increase electrical field efficiency, which tends to decrease along with a downsizing, can be cited, as in the case of a vibration piece which does not have a piezoelectric element. A vibrating arm which has a groove, or the like, is such that its rigidity decreases, it is not possible to obtain a stable flexural vibration by utilizing the characteristics of the base material of the vibrating arm, and a downsizing is difficult. Meanwhile, a flexural vibration piece which includes a piezoelectric element is such that the vibrating arm may be of a non-piezoelectric material, and the flexural vibration piece can be downsized while maintaining rigidity.
Furthermore, a flexural vibration piece (the tuning fork type vibrator in JP-A-2009-5022) wherein one piezoelectric element is provided over a wide area on the front surface of a vibrating arm, improving a so-called area efficiency, has been disclosed in, for example, JP-A-2009-5022. In this case, the vibrating arm of the flexural vibration piece synchronizes with the deformation direction of the piezoelectric element, and flexes in the same direction. As the vibrating arm has one piezoelectric element provided over a wide area, the piezoelectric element can maintain a high electrical field, and a further downsizing of the flexural vibration piece is possible. As heretofore described, according to a configuration wherein a piezoelectric element is provided on the front surface of a vibrating arm of a flexural vibration piece, the flexural vibration piece is such that a flexural vibration is obtained by utilizing the characteristics of the base material of the vibrating arm, and it is possible to achieve a downsizing.
However, with the heretofore technology, wires connecting electrodes provided on each vibrating arm, sandwiching the piezoelectric layer, are of a complex configuration adjacent to each other or intersecting across an insulating film. Also, with the configuration wherein a further pair of piezoelectric elements are provided on the rear surface on the side opposite the front surface of the vibrating arm, it can be supposed that the wires, although not specifically disclosed, are more complexly adjacent or intersecting. This kind of complex wiring is such that the intervals between wires narrow along with a downsizing of the flexural vibration piece and, in addition to an increase in parasitic capacity and a greater likeliness of crosstalk occurring, a considerable number of man-hours are needed for the formation of the wiring. Also, by thinning the vibration arm, another problem occurs in that the piezoelectric layer is more easily affected by the electrical field on the opposite surface, which may constitute a factor in impeding the downsizing of the flexural vibration piece.